1. Field of the Invention
The present invention relates to a printer employing therein an ink ribbon in the form of a tape.
2. Description of the Prior Art
Conventionally, in a printer to be used as a peripheral device of an electronic typewriter or a word processor, the positional relationship between a printing head and an ink ribbon is generally set unchanged.
When one or more letters, symbols and the like, for example, a string of characters ""Ay.sub.-- " are printed on a paper using such a printer, the ink ribbon 01 is used as shown in FIGS. 1a to 1d. In this example, a daisy wheel is used as the printing head.
A double quotation mark """ is located at an upper portion of one of the printing type pieces 02 of the daisy wheel. Accordingly, only an upper portion of the ink ribbon 01 is used, as shown in FIG. 1a. As a capital letter "A" is located at the center of a type piece 02, only the middle portion of the ink ribbon 01 is used, as shown in FIG. 1b. As a small letter "y" is located at a lower half of a type piece 02, only a lower half of the ink ribbon 01 is used, as shown in FIG. 1c. Furthermore, an underline ".sub.- " is located near the lower end of a type piece 02, so that only a portion near the lower end of the ink ribbon 01 is used, as shown in FIG. 1d.
FIG. 2 indicates how the ink ribbon 01 was used, resulting in printing marks which are completely identical with the printed condition on the paper. In other words, letters are printed using substantially the middle portion of the ink ribbon 01 whereas symbols are done using only the upper and lower portions of the ink ribbon 01. Accordingly, in the conventional printers, the letters and symbols can not be properly printed unless the ink ribbon 01 has a width h1 greater than a size obtained by adding a width required for printing all of the possible symbols required for printing the letters.
Because of this, users are obliged to use a relatively wide and expensive ribbon in the conventional printers rather than a relatively narrow and inexpensive ink ribbon.
Some of the conventional printers are capable of printing three lines at a time. Such printers, hereinafter referred to as three-line printers, do not require an ink ribbon having a width three times greater than the width h1 of the ink ribbon used for printing line by line but require an ink ribbon having a width h3 at least about two times greater than the latter, since upper and lower margins of the ink ribbon can be omitted. The three-line printers are controlled with respect to every three lines so as to print character by character in a direction of feed of a printing paper. To this end, the printing paper is fed line by line along with the ink ribbon so that the relative position of the ink ribbon may be shifted with respect to the printing head. FIG. 3 indicates printing marks formed on the ink ribbon 01 in a certain three-line printer. As is clear from the printing marks of FIG. 3, the three-line printers also can not employ a relatively narrow and inexpensive ink ribbon.